Building Evolutionary Architectures: Support Constant Change - Building Evolutionary Architectures: Support Constant Change -

Foreword Software Architecture Evolutionary Architecture How Is Long-term Planning Possible When Everything Changes All the Time?Once I’ve Built an Architecture, How Can I Prevent It from Gradually Degrading Over Time?Incremental Change Guided Change Multiple Architectural Dimensions Conway’s Law Why Evolutionary?Summary Fitness Functions What is a Fitness Function?Categories Atomic Versus Holistic Triggered Versus Continual Static Versus Dynamic Automated Versus Manual Temporal Intentional Over Emergent Domain-specific Identify Fitness Functions Early Review Fitness Functions Engineering Incremental Change Building Blocks Testable Deployment Pipelines CONTINUOUS INTEGRATION VERSUS DEPLOYMENT PIPELINES PENULTIMATEWIDGETS DEPLOYMENT PIPELINES QA IN PRODUCTION Combining Fitness Function Categories Case Study: Architectural Restructuring while Deploying 60 Times/Day Conflicting Goals Case Study: Adding Fitness Functions to PenultimateWidgets’ Invoicing Service Hypothesis- and Data-Driven Development Case Study: What to Port?Architectural Coupling Modularity Architectural Quanta and Granularity DOMAIN-DRIVEN DESIGN’S BOUNDED CONTEXT MONOLITHIC LISTING Evolvability of Architectural Styles Big Ball of Mud Monoliths Unstructured monoliths Layered architecture Modular monoliths Microkernel Event-Driven Architectures Brokers Mediators Service-Oriented Architectures ESB-driven SOA Microservices "SHARE NOTHING” AND APPROPRIATE COUPLING Service-based architectures "Serverless” Architectures Controlling Quantum Size Case Study: Guarding Against Component Cycles Evolutionary Data with contributions from Pramod Sadalage Evolutionary Database Design Evolving Schemas Shared Database Integration Option 1: No integration points, no legacy data Option 2: Legacy data, but no integration points Option 3: Existing data and integration points Inappropriate Data Coupling DBAS, VENDORS, AND TOOL CHOICES Two-Phase Commit Transactions Age and Quality of Data Case Study: Evolving PenultimateWidgets’ Routing Building Evolvable Architectures Mechanics Identify Dimensions Affected by Evolution Define Fitness Function(s) for Each Dimension Use Deployment Pipelines to Automate Fitness Functions Greenfield Projects Retrofitting Existing Architectures Appropriate Coupling and Cohesion Engineering Practices Fitness Functions REFACTORING VERSUS RESTRUCTURING COTS Implications Migrating Architectures Migration Steps Evolving Module Interactions Guidelines for Building Evolutionary Architectures Remove Needless Variability THE HAZARDS OF SNOWFLAKES Make Decisions Reversible Prefer Evolvable over Predictable Build Anticorruption Layers Case Study: Service Templates Build Sacrificial Architectures Mitigate External Change THE ELEVEN LINES OF CODE THAT BROKE THE INTERNET Updating Libraries Versus Frameworks Prefer Continuous Delivery to Snapshots Version Services Internally Case Study: Evolving PenultimateWidgets’ Ratings Evolutionary Architecture Pitfalls and Antipatterns Technical Architecture Antipattern: Vendor King Pitfall: Leaky Abstractions Antipattern: Last 10% Trap THE IBM SAN FRANCISCO PROJECT Antipattern: Code Reuse Abuse Case Study: Reuse at PenultimateWidgets Pitfall: Resume-Driven Development Incremental Change Antipattern: Inappropriate Governance FORCED DECOUPLING Case Study: Goldilocks Governance at PenultimateWidgets Pitfall: Lack of Speed to Release Business Concerns Pitfall: Product Customization Antipattern: Reporting Pitfall: Planning Horizons Putting Evolutionary Architecture into Practice Organizational Factors Cross-Functional Teams Organized Around Business Capabilities Product over Project AMAZON’S "TWO PIZZA” TEAMS Dealing with External Change Connections Between Team Members Team Coupling Characteristics Culture THREE STRIKES AND YOU REFACTOR Culture of Experimentation CFO and Budgeting Building Enterprise Fitness Functions CASE STUDY: LEGALITY OF OPEN SOURCE LIBRARIES Case Study: PenultimateWidgets as a Platform Where Do You Start?Low-Hanging Fruit Highest-Value Testing Infrastructure INFRASTRUCTURE CAN IMPACT ARCHITECTURE Case Study: Enterprise Architecture at PenultimateWidgets Future State?Fitness Functions Using AI Generative Testing Why (or Why Not)?Why Should a Company Decide to Build an Evolutionary Architecture?Predictable versus evolvable Scale Advanced business capabilities Cycle time as a business metric Isolating architectural characteristics at the quantum level Case Study: Selective Scale at PenultimateWidgets Adaptation versus evolution Why Would a Company Choose Not to Build an Evolutionary Architecture?Can’t evolve a ball of mud Other architectural characteristics dominate Sacrificial architecture Planning on closing the business soon Case Study: Consulting Judo The Business Case "The Future Is Already Here...”Moving Fast Without Breaking Things Less Risk New Capabilities Building Evolutionary Architectures